In a fabrication of a semiconductor device or a liquid crystal display, or the like, a substrate to be processed such as a semiconductor substrate, a glass substrate, or the like, is loaded into a processing vessel or a chamber of a processing device, and a film forming processing (chemical vapor deposition, etc.) or a microprocessing of a film (dry etching, etc.) is performed in an airtight or a depressurized chamber, wherein undesired particles are bound to be generated within the chamber. The production of these particles can be caused by the peeling off of reaction products that have been deposited within an inner wall of the chamber, or by growth of reaction products in the chamber, wherein the reaction products are generated by reaction between source gases (processing gases) introduced into the chamber or between a source gas and a material to be etched. These particles generated within the chamber are attached to a surface of the substrate to be processed, thereby causing a reduction in a production yield or deterioration of operating rate of the processing apparatus. Further, the effect of the particles on a process increases as the size of an element forming the semiconductor device or the display device becomes small, since as the size of the element becomes small, even a small particle as well as a large one begins to influence the process.
Conventionally, there have been proposed several kinds of methods for removing reaction products generated within the chamber as particles. Typically, a method for removing particles has been known, in which particles are collected on a negative potential electrode to thereby prevent the particles from falling onto a substrate to be processed, assuming that the particles are positively charged and generated within the chamber when completing a plasma etching (referring to reference 1).
FIG. 16 shows a particle-removing method disclosed in reference 1. A pair of electrodes 202 and 204 for producing a plasma is disposed parallel to each other inside a plasma etching apparatus 200, a lower electrode 202 is electrically connected to a high frequency power source 206 with a cathode coupling arrangement, and an upper electrode 204 is electrically grounded. In a top surface of the lower electrode 202, there is provided an electrostatic chuck electrode 212 of a positive potential via an insulator 210, and a substrate to be processed, e.g., a semiconductor substrate 208, is mounted on the electrostatic chuck electrode 212. A ring-shaped particle-removing electrode 214 is provided between the lower electrode 202 and the upper electrode 204 so as to surround an outer periphery of a plasma generation region. During a plasma etching, a processing gas, e.g., a halogen gas or the like, introduced from a gas inlet port 216 through a shower head 218 is excited into a plasma state between the lower electrode 202 and the upper electrode 204, and becomes a volatile gas by reaction with a material to be etched on a top surface of the semiconductor substrate 208, to thereby be exhausted to the outside of the chamber 200 through an exhaust port 220. The processing gas supply is stopped when the etching is completed, but positively charged particles start to fall off once a high frequency voltage applied being turned off. Accordingly, by applying a negative potential to the particle-removing electrode 214 from a DC power source 230, the positively charged particles are collected on the particle-removing electrode 214 of the negative potential, thereby preventing them from reaching the semiconductor substrate 208.
Another typical method for removing particles of a prior art has been known, in which the particles are negatively charged by a plasma during a plasma processing, and the negatively charged particles in the plasma are removed by a collecting electrode of a positive potential provided in the vicinity of a substrate to be processed (referring to reference 2). FIG. 17 describes the method disclosed in reference 2. Inside a chamber (not shown) of a parallel plate type plasma etching apparatus, there are disposed a lower electrode 300 and an upper electrode 302 parallel to each other, a semiconductor substrate 304 being mounted on the lower electrode 300. Further, a hollow or a tube-shaped collecting electrode 306 is provided in a ring shape around the lower electrode 300 so as to surround the substrate 304. The collecting electrode 306 has openings 307 in an inner peripheral surface thereof, and is connected through an exhaust pump (not shown) to outside the chamber via a gas exhaust path inside a stay 308. Preferably, in the collecting electrode 306, a fine particle attraction electrode (not shown) of a positive potential is provided inside the openings 307. Particles 312 that are negatively charged by a plasma 310 produced between the lower electrode 300 and the upper electrode 302 are collected through the openings 307 inside the collecting electrode 306, and exhausted through the gas exhaust path inside the stay 308 to the outside the chamber. As a result, theses particles 312 are prevented from being attached to the semiconductor substrate 304.
[reference 1] Japanese Patent Laid-Open Application No. 2000-3902 (paragraph [0043], FIG. 11)
[reference 2] WO 01/01467 (pages 9 and 10, FIG. 3)
In the conventional particle-removing method disclosed in reference 1, the positively charged particles are collected on the electrode of the negative potential when the plasma processing is completed, to thereby prevent the particles from being attached to the semiconductor substrate. However, the present inventors examined a behavior of a particle during a plasma processing by way of a particle measurement equipment (FIG. 4) to be mentioned later and found that particles were generated or existed even during the plasma processing, and further, uncharged particles, positively or negatively charged particles existed together (FIG. 7). This phenomenon can be evidently observed in a case of localizing a plasma by a magnetic field or the like, particularly. That is, in such a case, a gap between an inner wall of the chamber or a facing electrode for plasma excitation (for high frequency discharge) and a plasma becomes large, so that particles generated in this region float in an electrically neutral state. However, in the aforementioned prior art, the electrically neutral or negatively charged particles cannot be removed basically.
Further, in the method of reference 1, the particle-removing electrode 214 of the negative potential is disposed in a region where the positively charged particles are generated within the chamber. However, if a jig 214 of a metal member is disposed inside the chamber of the plasma processing apparatus, particularly, in the vicinity of the plasma generation region, a plasma is disturbed, whereby controlling a plasma distribution characteristic becomes difficult. Still further, there is a problem that the metal member may cause a metal contamination. Therefore, it is difficult to apply such a method disclosed in reference 1 to the plasma processing requiring a superior uniformity in a film thickness or an etching rate, or a high credibility of a process.
Meanwhile, in the particle-removing method disclosed in patent reference 2, the negatively charged particles during the plasma processing are removed through the collecting electrode of the positive potential. However, even in this method, uncharged and electrically neutral particles or positively charged particles cannot be removed basically. Further, same as reference 1, the collecting electrode 306 installed in the vicinity of the substrate 304 to be processed significantly disturbs a plasma state, and also, may cause a metal contamination. FIG. 17 shows a main part of the parallel plate type plasma etching apparatus of a cathode coupling mode. However, in a case of an anode coupling mode in which the lower electrode 300 is connected to a ground potential and the upper electrode 302 is connected to the high frequency power source via capacitance coupling, a plasma is produced more closely to the vicinity of the substrate to be processed 304. Thereby, controlling plasma becomes more difficult due to a disturbance by the collecting electrode 306. Further, if a dimension or an area of the substrate to be processed 304 is large, a distance between the collecting electrode 306 and a central portion of the substrate 304 becomes large. As a result, there is a difficulty in collecting the particles, which fall into the central portion of the substrate. For resolving such a problem, if the collecting electrode 306 is disposed close to the central portion of the substrate, a plasma disturbance becomes serious. Therefore, it is difficult to apply this method to a practical use.